Sensorless electric machine

ABSTRACT

An electric machine that includes a rotor core made of magnetic steel; a stator configured with stationary windings therein; openings disposed within or on the rotor core; and a rotor circuit that is configured to introduce saliency based on an orientation of part of the rotor circuit in relationship to a pole location of the electric machine, where the rotor circuit is made of a conductive, non-magnetic material. A rotor component and various embodiments of electric machines are also disclosed. The present invention has been described in terms of specific embodiment(s), and it is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the appending claims.

BACKGROUND OF THE INVENTION

The present invention relates generally to electric machines and moreparticularly to a sensorless electric machine, a component thereof,vehicles that employ the component and electric machine, and methods ofmaking and operating the same.

With an electric machine, be it an interior permanent magnet (IPM)machine, permanent magnet (PM) assisted synchronous reluctance machine(SRM), or an SRM, position is a critical informational element fortorque control at and near zero excitation frequency. Typically, anencoder, tachometer, or resolver is used with electric machines as theposition sensor.

However, the position sensor (e.g., encoder) along with its cabling andinterface electronics contributes a significant portion of the motordrive system cost and overall complexity and is often a majorreliability concern. Since the advent of the high frequency injectionmethod for zero frequency encoderless control, encoderless controls haveseen great improvements but none have found success in recovering thefull, or near full, torque capability of the machine. This is due toloss of small signal saliency at high-load levels for the machine.

Accordingly, there is an ongoing need for improvement of currentelectric machine technologies that address complexity, cost, efficiency,and/or performance.

BRIEF DESCRIPTION

The present invention overcomes at least some of the aforementioneddrawbacks by providing improvements that allow electric machines, suchas IPM motors to operate with full torque control without the need forany positions sensor (e.g., encoder). More specifically, the presentinvention is directed to a machine component and a machine that, whenemploying the component, is able to operate as a sensorless electricmachine. A vehicle that uses one or more electric machines and methodsof making and operating such an electric machine is/are also disclosed.

Therefore, in accordance with one aspect of the invention, a rotorcomponent comprises a rotor circuit configured for use with one of aninterior permanent magnet (IPM) machine and a synchronous reluctancemachine (SRM), the rotor circuit comprising: at least one pole circuit,wherein the at least one pole circuit are made of a conductive,non-magnetic material.

In accordance with another aspect of the invention, an electric machinecomprises a rotor core comprising magnetic steel; a stator configuredwith a plurality of stationary windings therein; a plurality of openingsdisposed within or on the rotor core; and a rotor circuit configured tointroduce saliency based on an orientation of a portion of the rotorcircuit in relationship to a pole location of the electric machine, saidrotor circuit made of a conductive, non-magnetic material.

In accordance with another aspect of the invention, an electric machinecomprises: a rotor core; a stator configured with a plurality ofstationary windings therein; a plurality of openings disposed within therotor core; and a rotor circuit structure comprising at least one polecircuit disposed in a predetermined location, wherein said predeterminedlocation is in range that extends from about a q-axis to about a d-axisof the electric machine.

In accordance with another aspect of the invention, an electric machinecomprising: a rotor core; a stator configured with a plurality ofstationary windings therein; a plurality of openings disposed within therotor core; a rotatable shaft therethrough; and a rotor circuitstructure comprising at least one loop or ring of a conductive,non-magnetic material, wherein said at least one loop or ring issubstantially concentric about a d-axis of the electric machine.

In accordance with another aspect of the invention, an interiorpermanent magnet (IPM) machine comprises a means for convertingelectrical energy to rotational energy; and a means for providingincreased magnetic saliency at high frequency excitation.

Various other features and advantages of the present invention will bemade apparent from the following detailed description and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a perspective view of a rotor circuit structure componentaccording to an embodiment of the present invention.

FIG. 2 is a perspective view of rotor core of an electric machineincorporating a rotor circuit structure component according to anembodiment of the present invention.

FIG. 3A is a top view of a portion of a rotor lamination and rotorcircuit structure component according to an embodiment of the presentinvention.

FIG. 3B is a schematic perspective diagram of the rotor circuitstructure component in FIG. 3A according to an embodiment of the presentinvention.

FIG. 4A is a top view of a portion of a rotor lamination and rotorcircuit structure component according to another embodiment of thepresent invention.

FIG. 4B is a schematic perspective diagram of the rotor circuitstructure component in FIG. 4A according to an embodiment of the presentinvention.

FIG. 5A is a top view of a portion of a rotor lamination and rotorcircuit structure component according to another embodiment of thepresent invention.

FIG. 5B is a schematic perspective diagram of the rotor circuitstructure component in FIG. 5A according to an embodiment of the presentinvention.

FIG. 6A is a top view of a portion of a rotor lamination and rotorcircuit structure component according to another embodiment of thepresent invention.

FIG. 6B is a schematic perspective diagram of the rotor circuitstructure component in FIG. 6A according to an embodiment of the presentinvention.

FIG. 7A is a top view of a portion of a rotor lamination and rotorcircuit structure component according to another embodiment of thepresent invention.

FIG. 7B is a schematic perspective diagram of the rotor circuitstructure component in FIG. 7A according to an embodiment of the presentinvention.

FIG. 8A is a top view of a portion of a rotor lamination and rotorcircuit structure component according to another embodiment of thepresent invention.

FIG. 8B is a schematic perspective diagram of the rotor circuitstructure component in FIG. 8A according to an embodiment of the presentinvention.

FIG. 9A is a top view of a portion of a rotor lamination and rotorcircuit structure component according to another embodiment of thepresent invention.

FIG. 9B is a schematic perspective diagram of the rotor circuitstructure component in FIG. 9A according to an embodiment of the presentinvention.

FIGS. 10A, 10B, and 10C are schematic diagrams showing perspective viewsof a rotor circuit structure component according to embodiments of thepresent invention.

FIG. 11 is a schematic diagram of a top view of a portion of a rotorcircuit structure component according to an embodiment of the presentinvention.

FIG. 12A is a schematic diagram of a top view of a portion of a rotorcircuit structure component according to an embodiment of the presentinvention.

FIG. 12B is top view of a portion of a rotor lamination and the rotorcircuit structure component of FIG. 12A according to another embodimentof the present invention.

FIG. 13 is a schematic diagram of a top view of a portion of a rotorcircuit structure component according to an embodiment of the presentinvention.

FIG. 14A is a schematic diagram of a top view of a portion of a rotorcircuit structure component according to an embodiment of the presentinvention.

FIG. 14B is top view of a portion of a rotor lamination and the rotorcircuit structure component of FIG. 14A according to another embodimentof the present invention.

FIG. 15 is top view of a portion of a rotor lamination and the rotorcircuit structure component according to another embodiment of thepresent invention.

FIG. 16 is top view of a portion of a rotor lamination and the rotorcircuit structure component according to another embodiment of thepresent invention.

FIG. 17A is schematic diagram showing a perspective view of a partialinstallation of a portion of a rotor circuit structure component in arotor portion of a machine according to an embodiment of the presentinvention.

FIG. 17B is schematic diagram showing a perspective view of a completedinstallation embodiment shown in FIG. 17A.

FIG. 18 is schematic diagram showing a perspective view of a completedinstallation of a portion of a rotor circuit structure component in arotor portion of a machine according to another embodiment of thepresent invention.

FIG. 19 is schematic diagram showing a perspective view of a completedinstallation of a portion of a rotor circuit structure component in arotor portion of a machine according to another embodiment of thepresent invention.

FIG. 20 is a schematic diagram showing a perspective view of a rotorcircuit structure component according to another embodiment of thepresent invention.

FIG. 21 is a graph illustrating small signal saliency for electricmachine of the related art.

FIG. 22 is a graph illustrating small signal saliency for an electricmachine with a rotor circuit structure, according to an embodiment ofthe present invention.

FIG. 23 is a graph illustrating small signal saliency angle for electricmachine of the related art.

FIG. 24 is a graph illustrating small signal saliency angle for anelectric machine with a rotor circuit structure, according to anembodiment of the present invention.

FIG. 25 is a schematic graph comparing motor speed and torque for arelated art machine (without a rotor structure) and a machine with arotor circuit structure, according to an embodiment of the presentinvention.

DETAILED DESCRIPTION

Unless defined otherwise, technical and scientific terms used hereinhave the same meaning as is commonly understood by one of ordinary skillin the art with respect to the presently disclosed subject matter. Theterms “first”, “second”, and the like, as used herein do not denote anyorder, quantity, or importance, but rather are used to distinguish oneelement from another. The terms “a”, “an”, and “the” do not denote alimitation of quantity, but rather denote the presence of at least oneof the referenced item, and the terms “front”, “back”, “bottom”, and/or“top”, unless otherwise noted, are used for convenience of descriptiononly, and are not limited to any one position or spatial orientation.

If ranges are disclosed, the endpoints of all ranges directed to thesame component or property are inclusive and independently combinable(e.g., ranges of “up to about 25 wt. %,” is inclusive of the endpointsand all intermediate values of the ranges of “about 5 wt. % to about 25wt. %,” etc.). The modified “about” used in connection with a quantityis inclusive of the stated value and has the meaning dictated by thecontext (e.g., includes the degree of error associated with measurementof the particular quantity). Accordingly, the value modified by the term“about” is not necessarily limited only to the precise value specified.

As used herein, the term “Pole Circuit” means one or more circuits thatis affiliated with one pole of the electric machine. The one or morecircuits may comprise one ring/loop, multiple rings/loops, one loop/ringof a cage, or one loop/ring of a cage with one or more innerrings/loops. The cage may be a shifted or non-shifted cage. Rings/loopsmay be shifted or non-shifted.

As used herein, the term “Shifted Cage” means one or more connectedrings or loops wherein a rotor conductor (or if more than one rotorconductor are adjacent, then a midpoint between the plurality ofadjacent rotor conductors) is not aligned with a q-axis of the machine,but instead is shifted by a distance from the q-axis. Contrastingly, acage that is not shifted has a rotor conductor (or if more than onerotor conductor are adjacent, then a midpoint between the plurality ofadjacent rotor conductors) that is aligned with the q-axis of themachine.

Aspects of the present invention have been shown to offer advantagesover previous electric machine constructs. Aspects of the presentinvention provide design features for an electric machine (e.g., IPMmotor) that enables full torque control without the use of any positionsensor. An aspect of the present invention includes the use of acomponent, termed herein a special rotor structure that introducesmagnetic saliency for high frequency excitation, wherein this highfrequency excitation can be used for sensorless (e.g., encoderless)motor control. The rotor structure introduces electrical circuits(shorted circuit, closed circuit with passive or active elements) tospecific orientation of the rotor so that it couples with the statorwinding magnetically. The position of the rotor is measured by applyinghigh frequency carrier voltage to the stator and by indirectly measuringthe current of the rotor, by measuring the (reflected) high frequencycarrier current response in the stator. If the rotor circuit is alignedin phase with the high frequency injection the impedance of the motor isreduced. This variation of impedance is used to track rotor position. Asa result, small signal saliency up to necessary loading level isintroduced and maintained without impact on electric machineperformance, efficiency, and reliability.

Referring to FIG. 1 a rotor circuit or electrical component 10incorporating aspects of the present invention is shown. The component10 may comprise one or more rotor conductors (e.g., rotor bars 14)connected to one or more connection elements 16. As shown, the rotorbars 14 are substantially longitudinal in configuration. As will bediscussed herein the component 10 and the rotor bars 14 and connectionelements 16 are configured so as to substantially surround permanentmagnets 40 located in an electric machine 100. In this manner two ormore rotor bars 14 are connected to two or more connection elements 16such that they define a loop or ring 12. While the embodiment in FIG. 1clearly shows a quantity of four rings 12 each ring 12 comprising tworotor bars 14 and two connection elements 16, other quantities andconfigurations of elements of the component 10 are suitable withoutdeparting from the present invention. For example, the component 10 maycomprise four rotor bars 14 and a plurality of connection elements 16are either end of the component 10, thereby defining a cage 13.Similarly, in another embodiment, the component 10 may comprise aplurality of loops or rings 12, wherein each ring 12 comprises fourrotor bars 14 and two connection elements 16. In still otherembodiments, the ring(s) 12 and/or cage 13 may comprise virtually anyquantity of conductors and/or connection elements.

The rotor bars 14 and connection elements 16 may be made of any suitableconductive, non-magnetic material, or combinations thereof. By examplebut not limitation, the rotor bars 14 and connection elements 16 may becastings made of aluminum, copper, alloys of copper or aluminum, orother suitable material or combination of materials.

It should be noted that although several of the embodiments discussedherein discuss the use of rotor bars, other conductive elements may beused in the component 10 without departing from the invention. Forexample, any suitable rotor conductor may be substituted in lieu of therotor bars 14 that are discussed herein for the various embodiments.Other conductive elements for use in lieu of the rotor bars 14 and/orthe connection elements 16 include, but are not limited to, one or moreof multistranded bars, multi-stranded wire, litz wire, and combinationsthereof.

Similarly, the rotor bar 14 has a cross-sectional shape that is suitableto address design factors including skin effect, cooling surface,structural strength, EM fitness, and the like. Suitable shapes for thecross-section of the rotor bar include a circle, square, rectangle, andthe like.

The end perspective view of another embodiment of the component 10located in rotor portion of a motor 100 is shown in FIG. 2. The motor100 includes a plurality of rotor core laminations 20 stacked so as toform a rotor core 90. As shown, in the end view where a cover plate isomitted for illustrative purposes only so as to allow a first rotor corelamination 20 to be viewed. The rotor core lamination 20 includes aplurality of openings 22. Permanent magnets 40 may be located within theplurality of openings 22. For illustrative purposes only the permanentmagnets 40 are shown disposed in only one set (e.g., at one pole) ofopenings 22. The other three sets of openings 22 (i.e., four-polemachine) are shown without permanent magnets 40 therein. At the centerof the rotor core lamination 20 is a shaft opening 94 configured toreceive a rotatable shaft (not shown). As depicted, the component 10 issimilar to the embodiment shown in FIG. 1 and comprises a quantity offour rings or loops 12, each comprising two rotor bars 14 connected totwo connection elements 16. In this manner, two of the rotor bars 14 andthe two connection elements 16 are interconnected so as to form a rotorring or loop 12. Four rotor rings or loops 12 are formed as part of thecomponent 10 in this manner so as to match the quantity of poles (i.e.,four) in the embodiment of the motor shown 100.

Referring collectively to FIGS. 3A and 3B, a top view of a portion of arotor lamination 20 portion of an electric machine 100 with a component10 and a schematic diagram of a perspective view of the component 10from FIG. 3A are shown respectively. FIG. 3A depicts a rotor lamination20 of a single layer, four-pole IPM 100 having straight permanentmagnets 40 therein. FIG. 3B depicts a rotor component 10 that may betermed a four-loop configuration. As shown and known in the art, therotor lamination 20 includes a plurality of openings 22 that, dependingon the particular embodiment, may have disposed therein one or morepermanent magnets 40. Once the permanent magnets 40 are disposed withinthe openings 22 there typically remains adjacent to either end of thepermanent magnets 40 an opening, or remaining opening, 24. Forillustrative purposes only, the stator and/or stator windings are notshown that substantially surround the rotor component.

The plurality of rotor bars 14 are disposed in the plurality of openings24 longitudinally through the stack of rotor laminations 20. At or neareither end of the stack of rotor laminations 20 are connection elements16 that are connected to both ends of the rotor bars 14. In this manner,the component 10 embodiment in FIG. 3B has four rotor loops 12 eachconstructed of two rotor bars 14 and two connection elements 16, therebymatching the quantity of poles (i.e., four) for the particular machine100.

Referring collectively to FIGS. 4A and 4B, a top view of a portion of arotor lamination 20 portion of an electric machine 100 with a component10 and a schematic diagram of a perspective view of the component 10from FIG. 4A are shown respectively. FIG. 4A depicts a rotor lamination20 of a single layer, four-pole IPM 100 having straight permanentmagnets 40 therein. FIG. 4B depicts a rotor component 10 that may betermed a four-loop, shifted-ring configuration. As shown and known inthe art, the rotor lamination 20 includes a plurality of openings 22that, depending on the particular embodiment, may have disposed thereinone or more permanent magnets 40. Once the permanent magnets 40 aredisposed within the openings 22 there typically remains adjacent toeither end of the permanent magnets 40 an opening, or remaining opening,24. For illustrative purposes only, the stator and/or stator windingsare not shown that substantially surround the rotor component.

The plurality of rotor bars 14 are disposed in some of the plurality ofopenings 24 longitudinally through the stack of rotor laminations 20. Inthis embodiment two adjacent rotor bars 14 are co-located in a singleopening 24 while the opening 24 at the other end of the magnet 40 isleft unfilled. At or near either end of the stack of rotor laminations20 are connection elements 16 that are connected to both ends of therotor bars 14. In this manner, the component 10 embodiment in FIG. 4Bhas four rotor loops 12 each constructed of two rotor bars 14 and twoconnection elements 16, thereby matching the quantity of poles (i.e.,four) for the particular machine 100. By co-locating the two rotor bars14 from adjacent poles, the four loops 12 are effectively connected toeach other, thereby forming shifted rings 13.

Referring collectively to FIGS. 5A and 5B, a top view of a portion of arotor lamination 20 portion of an electric machine 100 with a component10 and a schematic diagram of a perspective view of the component 10from FIG. 5A are shown respectively. FIG. 5A depicts a rotor lamination20 of a single layer, four-pole IPM 100 having straight permanentmagnets 40 therein. FIG. 5B depicts a rotor component 10 that may betermed a four-loop, shifted-cage configuration, similar to theembodiment shown in FIGS. 4A and 4B. As shown and known in the art, therotor lamination 20 includes a plurality of openings 22 that, dependingon the particular embodiment, may have disposed therein one or morepermanent magnets 40. Once the permanent magnets 40 are disposed withinthe openings 22 there typically remains adjacent to either end of thepermanent magnets 40 an opening, or remaining opening, 24. Forillustrative purposes only, the stator and/or stator windings are notshown that substantially surround the rotor component.

The plurality of rotor bars 14 are disposed in some of the plurality ofopenings 24 longitudinally through the stack of rotor laminations 20. Inthis embodiment instead of co-locating two adjacent rotor bars 14 in asingle opening 24 (as done in FIG. 4A), the two adjacent rotor bars 14are combined into a single rotor bar 14. Again, the opening 24 at theother end of the magnet 40 is left unfilled. At or near either end ofthe stack of rotor laminations 20 are connection elements 16 that areconnected to both ends of the rotor bars 14. In this manner, thecomponent 10 embodiment in FIG. 5B has four rotor loops 12 eachconstructed of two rotor bars 14 and two connection elements 16, therebymatching the quantity of poles (i.e., four) for the particular machine100. However, the quantity of total rotor bars 14 is less due to theeffective sharing of rotor bars 14 from the adjacent loops 12 (andpoles). The component 10 has eight connection elements 16 but four rotorbars 14 for use in a four pole machine 100. By cross connecting adjacentloops 12 with the connection elements 16 from adjacent poles, the fourloops 12 are effectively connected to each other, thereby forming acage, or shifted cage 13.

Referring collectively to FIGS. 6A and 6B, a top view of a portion of arotor lamination 20 portion of an electric machine 100 with a component10 and a schematic diagram of a perspective view of the component 10from FIG. 6A are shown respectively. FIG. 6A depicts a rotor lamination20 of a spoke-type, four-pole IPM 100 having straight permanent magnets40 therein. FIG. 6B depicts a rotor component 10 that may be termed afour-loop configuration. As shown and known in the art, the rotorlamination 20 includes a plurality of openings 22 that, depending on theparticular embodiment, may have disposed therein one or more permanentmagnets 40. Once the permanent magnets 40 are disposed within theopenings 22 there typically remains adjacent to either end of thepermanent magnets 40 an opening, or remaining opening, 24. Forillustrative purposes only, the stator and/or stator windings are notshown that substantially surround the rotor component.

The plurality of rotor bars 14 are disposed in the plurality of outboardopenings 24 longitudinally through the stack of rotor laminations 20. Ator near either end of the stack of rotor laminations 20 are connectionelements 16 that are connected to both ends of the rotor bars 14. Inthis manner, the component 10 embodiment in FIG. 6B has four rotor loops12 each constructed of two rotor bars 14 and two connection elements 16,thereby matching the quantity of poles (i.e., four) for the particularmachine 100.

Referring collectively to FIGS. 7A and 7B, a top view of a portion of arotor lamination 20 portion of an electric machine 100 with a component10 and a schematic diagram of a perspective view of the component 10from FIG. 7A are shown respectively. FIG. 7A depicts a rotor lamination20 of a spoke-type, four-pole IPM 100 having straight permanent magnets40 therein. FIG. 7B depicts a rotor component 10 that may be termed afour-loop, rotor cage configuration, similar in aspects to theembodiment shown in FIGS. 6A and 6B. As shown and known in the art, therotor lamination 20 includes a plurality of openings 22 that, dependingon the particular embodiment, may have disposed therein one or morepermanent magnets 40. Once the permanent magnets 40 are disposed withinthe openings 22 there typically remains adjacent to either end of thepermanent magnets 40 an opening, or remaining opening, 24. Forillustrative purposes only, the stator and/or stator windings are notshown that substantially surround the rotor component.

The plurality of rotor bars 14 are disposed in the outboard plurality ofopenings 24 longitudinally through the stack of rotor laminations 20. Inthis embodiment instead of co-locating two adjacent rotor bars 14 in asingle opening 24 (as done in FIG. 6A), the two adjacent rotor bars 14are combined into a single rotor bar 14. At or near either end of thestack of rotor laminations 20 are connection elements 16 that areconnected to both ends of the rotor bars 14. In this manner, thecomponent 10 embodiment in FIG. 7B has four rotor loops 12 eachconstructed of two rotor bars 14 and two connection elements 16, therebymatching the quantity of poles (i.e., four) for the particular machine100. However, the quantity of total rotor bars 14 is less due to theeffective sharing of rotor bars 14 from the adjacent loops 12 (andpoles). The component 10 thus comprises eight connection elements 16 butfour rotor bars 14 total for use in a four pole machine 100. By crossconnecting adjacent loops 12 with the connection elements 16 fromadjacent poles, the four loops 12 are effectively connected to eachother, thereby forming a cage 13.

Referring collectively to FIGS. 8A and 8B, a top view of a portion of arotor lamination 20 portion of an electric machine 100 with a component10 and a schematic diagram of a perspective view of the component 10from FIG. 8A are shown respectively. FIG. 8A depicts a rotor lamination20 of a multi-layer, four-pole IPM 100 having straight permanent magnets40 therein. FIG. 8B depicts a rotor component 10 that may be termed afour-loop configuration. As shown and known in the art, the rotorlamination 20 includes a plurality of openings 22 that, depending on theparticular embodiment, may have disposed therein one or more permanentmagnets 40. Once the permanent magnets 40 are disposed within theopenings 22 there typically remains adjacent to either end of thepermanent magnets 40 an opening, or remaining opening, 24. Forillustrative purposes only, the stator and/or stator windings are notshown that substantially surround the rotor component. As withmulti-layer IPM, there is typically a plurality of rows of openings 22and permanent magnets 40 therein located for each pole.

The plurality of rotor bars 14 are disposed in the plurality of openings24 longitudinally through the stack of rotor laminations 20. At or neareither end of the stack of rotor laminations 20 are connection elements16 that are connected to both ends of the rotor bars 14. In this manner,the component 10 embodiment in FIG. 8B has four rotor loops 12 eachconstructed of two rotor bars 14 and two connection elements 16, therebymatching the quantity of poles (i.e., four) for the particular machine100. In this particular embodiment, the rotor bars 14 are located in thefurthest inboard openings 24 of the multi-layer rotor lamination 20. Itshould be apparent, that the rotor bars could be located in otheropenings 24 of the lamination 20.

Referring collectively to FIGS. 9A and 9B, a top view of (an entire)portion of a rotor lamination 20 portion of an electric machine 100 witha component 10 and a schematic diagram of a perspective view of thecomponent 10 from FIG. 9A are shown respectively. FIG. 9A depicts arotor lamination 20 of a multi-layer, four-pole IPM 100 having straightpermanent magnets 40 therein. FIG. 9B depicts a rotor component 10 thatmay be termed a four-loop, cage or shifted-cage configuration. As shownand known in the art, the rotor lamination 20 includes a plurality ofopenings 22 that, depending on the particular embodiment, may havedisposed therein one or more permanent magnets 40. Once the permanentmagnets 40 are disposed within the openings 22 there typically remainsadjacent to either end of the permanent magnets 40 an opening, orremaining opening, 24. For illustrative purposes only, the stator and/orstator windings are not shown that substantially surround the rotorcomponent. As with multi-layer IPM, there is typically a plurality ofrows of openings 22 and permanent magnets 40 therein located for eachpole.

The plurality of rotor bars 14 are disposed in the plurality of openings24 longitudinally through the stack of rotor laminations 20. In thisconfiguration only a single rotor bar 14 is placed in an opening 24 ineach pole (See FIG. 9A). At or near either end of the stack of rotorlaminations 20 are connection elements 16 that are connected to bothends of the rotor bars 14. The connection element 16 connects a rotorbar 14 from a first pole to the rotor bar 14 of an adjacent pole,thereby shifting the element 10. In this manner, the component 10embodiment in FIG. 9B has four rotor loops 12 each constructed of tworotor bars 14 and two connection elements 16, thereby matching thequantity of poles (i.e., four) for the particular machine 100. However,due to the shifted-cage configuration of the embodiment, only four rotorbars 14 total and eight connection elements 16 are required for afour-pole machine 100 such as that depicted. In this particularembodiment, the rotor bars 14 are located in the furthest inboardopenings 24 of the multi-layer rotor lamination 20. It should beapparent, that the rotor bars could be located in other openings 24 ofthe lamination 20.

Referring collectively to FIGS. 10A, 10B, and 10C, schematic diagrams ofperspective views of components 10 according to aspects of the presentinvention are shown. The figures are provided to show various schematicembodiments to show the general positional relationship between variouselements of the component 10 and a d-axis and q-axis of a machine (not)that may employ the component 10. The d-axis (direct axis) and theq-axis (quadrature axis) are denoted by arrows labeled “d” and “q”,respectively. As shown in FIG. 10A, a component 10 includes four rotorloops or rings 12. Each ring 12 comprises two rotor bars 14 connected ateach end to a connector element 16. Rotor bars 14 are effectively sharedby adjacent rings 12 so that all four rings 12 are connected. There area total of four rotor bars 14 for the element 10. Because the rotor bars14 are effectively shared by adjacent poles or the component 10, onlyfour rotor bars 14 are needed by the component 10 for use with afour-pole machine (not shown). In this manner, the four loops 12, beinginterconnected, effectively define a cage 13. As shown, the approximatemidpoint of the loop 12 aligns with the d-axis. In other words, a loop12 is substantially concentric with the d-axis. Similarly, the q-axismay substantially align with a rotor bar 14.

As shown in FIG. 10B, the four rings 12 are not interconnected as in theembodiment shown in FIG. 10A. Each ring 12 comprises two rotor bars 14and two connector elements 16. As shown, and as with the embodiment inFIG. 10A, the approximate midpoint of the loop 12 aligns with thed-axis. In other words, a loop 12 is substantially concentric with thed-axis. Similarly, the q-axis may substantially align with a conceptualline or axis between two adjacent rotor bars 14.

Referring to the embodiment shown in FIG. 10C, the element 10 comprisesfour rotor loops or rings 12. Each ring 12 comprises two rotor bars 14connected at each end to a connector element 16. Rotor bars 14 areeffectively shared by adjacent rings 12 so that all four rings 12 areconnected, effectively defining a shifted cage 13 configuration. Thus,there are a total of four rotor bars 14 for the element 10. As shown,and as with the embodiments in FIGS. 10A and 10B, the approximatemidpoint of the loop 12 aligns with the d-axis. In other words, a loop12 is substantially concentric with the d-axis. However, in theembodiment shown in FIG. 10C, the rotor bar 14 does not align with theq-axis but is shifted by a certain angle (or distance) from the q-axis.

As shown in FIGS. 10A-10C, each embodiment is configured such that thed-axis aligns about with the midpoint of connector element 16. That is aloop 12 or plurality of inner loops may be substantially concentric withthe d-axis. However, depending on the embodiment the rotor bar 14 or anequidistant axis between adjacent rotor bars 14 may align with theq-axis a shown in FIGS. 10A and 10B, respectively. Contrastingly, asshown for example in FIG. 10C, the rotor bar 14 or an equidistant axisbetween adjacent rotor bars 14 may be offset, or shifted, from beingaligned with the q-axis. The embodiments shown are configured for use ina four-pole machine 100. It should be apparent to one skilled in the artthat other configurations of elements 10 are allowed without departingfrom aspects of the present invention. For example, an element 10configured for use in an eight-pole machine 100 would contrastingly haveat least eight rotor bars 14. In embodiments of the present invention,the quantity of rotor bars 14 would equal the quantity of poles of themachine 100 (see e.g., FIGS. 10A and 10C). Contrastingly, in otherembodiments, such as the element 10 shown in FIG. 10B, the quantity ofrotor bars 14 (e.g., eight) may be double the quantity of poles (e.g.,four) of the machine 100. Clearly, other configurations of elements 10that have differing quantities of rotor bars 14 in view of quantity ofpoles of the machine 100 in which the element 10 is configured for areavailable under aspects of the present invention without departing fromthe intent of the invention.

Referring to FIGS. 11 and 12A, schematic diagrams of top views of aportion of a rotor structure component 10 according to embodiments ofthe present invention are shown. (These schematic views are such thateffectively it is as if the component 10 were opened and rolled outflat, in a planar fashion, on the plane of the page). The component 10comprises a plurality of rotor bars 14 connected to a plurality ofconnection elements 16. The component 10 in FIG. 11 comprises a singlering 12 per pole of the machine 100 (not shown). The two adjacent rotorbars 14 align with the q-axis and the approximate midpoint of the ring12 aligns with the d-axis. That is the ring 12 on the right side in theFIG. 11 is substantially concentric with the d-axis. Alternatively, thecomponent 10 of FIG. 12A comprise multiple rings 12 per pole of themachine 100 (not shown). Multiple rings 12 can further assist in furtherincreasing saliency. There are three rings 12 per pole on the component10 shown. The outermost two adjacent rotor bars 14 of the rings 12 alignwith the q-axis and the approximate midpoints of the multiple rings 12align with the d-axis. That is the rings 12 on the right side in theFIG. 12A are substantially concentric with the d-axis. It should beapparent that although three rings 12 are depicted, other configurationsand quantities are allowable without departing from aspects of thepresent invention.

Referring to FIG. 12B, a top view of a portion of a rotor lamination 20portion of an electric machine 100 with a component 10 and a schematicdiagram of a perspective view of the component 10 from FIG. 12A isshown. FIG. 12B depicts a rotor lamination 20 of a multi-layer,four-pole IPM 100 having straight permanent magnets 40 therein. Someattributes of the embodiment shown are similar to the embodiment shownin FIG. 8A. As shown and known in the art, the rotor lamination 20includes a plurality of openings 22 that, depending on the particularembodiment, may have disposed therein one or more permanent magnets 40.Once the permanent magnets 40 are disposed within the openings 22 theretypically remains adjacent to either end of the permanent magnets 40 anopening, or remaining opening, 24. For illustrative purposes only, thestator and/or stator windings are not shown that substantially surroundthe rotor component. As with multi-layer IPM, there is typically aplurality of rows of openings 22 and permanent magnets 40 thereinlocated for each pole.

The plurality of rotor bars 14 are disposed in the plurality of openings24 longitudinally through the stack of rotor laminations 20. At or neareither end of the stack of rotor laminations 20 are connection elements16 that are connected to both ends of the rotor bars 14. In this manner,the component 10 embodiment in FIG. 12B has four rotor loops 12 eachconstructed of two rotor bars 14 and two connection elements 16, therebymatching the quantity of poles (i.e., four) for the particular machine100. However, there are two inner rings or loops 12 for each ring orloop 12 (See FIG. 12A). As shown, the rotor bars 14 for each of the twoinner rings or loops 12 also are inserted into the openings 24 adjacentto magnets 40.

Referring to FIGS. 13 and 14A, schematic diagrams of top views of aportion of a rotor structure component 10 according to embodiments ofthe present invention are shown. (These schematic views are such thateffectively it is as if the component 10 were opened and rolled outflat, in a planar fashion, on the plane of the page). The component 10comprises a plurality of rotor bars 14 connected to a plurality ofconnection elements 16. The rotor bars 14 are shared by adjacent loopsor rings 12. As such the rings 12 collectively form a cage 13. Thecomponent 10 in FIG. 13 comprises a cage 13 with a single loop 12 perpole of the machine 100 (not shown). The single, shared rotor bar 14aligns with the q-axis and the approximate midpoint of the loops 12 ofthe cage 13 aligns with the d-axis. That is the ring 12 of the cage 13on the right side in the FIG. 13 is substantially concentric with thed-axis. Alternatively, the component 10 of FIG. 14A comprise a cage 13also having multiple inner rings 12 per pole of the machine 100 (notshown). The additional multiple rings 12 can further assist in furtherincreasing saliency. There are two inner rings 12 per pole on thecomponent 10 in addition to the cage 13. The shared rotor bar 14 of thecage 13 aligns with the q-axis and the approximate midpoints of themultiple inner rings 12 and the cage 13 align with the d-axis. That isthe rings 12 and the cage 13 on the right side in the FIG. 14A issubstantially concentric with the d-axis. It should be apparent thatalthough two rings 12 are depicted in addition to the cage 13, otherconfigurations and quantities are allowable without departing fromaspects of the present invention.

Referring to FIG. 14B, a top view of a portion of a rotor lamination 20portion of an electric machine 100 with a component 10 and a schematicdiagram of a perspective view of the component 10 from FIG. 14A isshown. FIG. 14B depicts a rotor lamination 20 of a combinationmulti-layer/spoke-type, four-pole IPM 100 having straight permanentmagnets 40 therein. Some attributes of the embodiment shown are similarto the embodiments shown in both FIG. 7A and FIG. 8A. As shown and knownin the art, the rotor lamination 20 includes a plurality of openings 22that, depending on the particular embodiment, may have disposed thereinone or more permanent magnets 40. Once the permanent magnets 40 aredisposed within the openings 22 there typically remains adjacent toeither end of the permanent magnets 40 an opening, or remaining opening,24. For illustrative purposes only, the stator and/or stator windingsare not shown that substantially surround the rotor component. As withmulti-layer IPM, there is typically a plurality of rows of openings 22and permanent magnets 40 therein located for each pole. As shown, thespoke-type aspect of the IPM 100 also includes magnets 40 that areradially disposed in a plurality of openings 22. Once the permanentmagnets 40 are disposed within the openings 22 there typically remainsadjacent to either end of the permanent magnets 40 an opening 24.

The plurality of rotor bars 14 are disposed in the plurality of openings24 longitudinally through the stack of rotor laminations 20. At or neareither end of the stack of rotor laminations 20 are connection elements16 that are connected to both ends of the rotor bars 14. As shown inFIG. 14A, the outer rings 12 share common rotor bars 14, therebydefining a cage 13. In this manner, the component 10 embodiment in FIG.14B has four rotor loops 12 each constructed of two rotor bars 14 andtwo connection elements 16, thereby matching the quantity of poles(i.e., four) for the particular machine 100. The four rotor loops 12sharing common rotor bars 14 thereby defines a cage 13. Thus, the cage13 may be formed of four rotor bars 14 and eight total connectorelements 16. However, there are also two inner rings or loops 12 foreach outer ring or loop 12 (See FIG. 14A). As shown, the rotor bars 14for each of the two inner rings or loops 12 also are inserted into theopenings 24 adjacent to magnets 40. The rotor bars 14 for the cage 13may be inserted in the openings 24 adjacent to the spoke-type magnets40. The rotor bars 14 for the two inner loops or rings 12 may beinserted in the openings 24 adjacent to the multi-layer type magnets 40.

Referring to FIG. 15, a top view of (an entire) portion of a rotorlamination 20 portion of an electric machine 100 with a component 10 isshown. FIG. 15 depicts a rotor lamination 20 of a multi-layer, four-poleIPM 100 having straight permanent magnets 40 therein. This embodiment issimilar in some aspects to the embodiments illustrated in FIGS. 9A and9B and the FIGS. 14A and 14B. The rotor component 10 may be termed ashifted-cage with inner rings or loops configuration. As shown and knownin the art, the rotor lamination 20 includes a plurality of openings 22that, depending on the particular embodiment, may have disposed thereinone or more permanent magnets 40. Once the permanent magnets 40 aredisposed within the openings 22 there typically remains adjacent toeither end of the permanent magnets 40 an opening, or remaining opening,24. For illustrative purposes only, the stator and/or stator windingsare not shown that substantially surround the rotor component. As withmulti-layer IPM, there is typically a plurality of rows of openings 22and permanent magnets 40 therein located for each pole.

The plurality of rotor bars 14 are disposed in the plurality of openings24 longitudinally through the stack of rotor laminations 20. In thisconfiguration only a single rotor bar 14 is placed in an opening 24 ineach pole (See FIG. 9A). At or near either end of the stack of rotorlaminations 20 are connection elements 16 that are connected to bothends of the rotor bars 14. The connection element 16 connects a rotorbar 14 from a first pole to the rotor bar 14 of an adjacent pole,thereby shifting the element 10 creating a shifted cage 13configuration. In this manner, the component 10 embodiment has fourrotor loops 12 each constructed of two rotor bars 14 and two connectionelements 16, thereby matching the quantity of poles (i.e., four) for theparticular machine 100. However, due to the shifted-cage configurationof the embodiment, only four rotor bars 14 total and eight connectionelements 16 are required for a four-pole machine 100 such as thatdepicted. In this particular embodiment, the rotor bars 14 are locatedin the furthest inboard openings 24 of the multi-layer rotor lamination20. It should be apparent, that the rotor bars could be located in otheropenings 24 of the lamination 20. In addition, there are two additionalinner loops 12 for each pole that are shifted in their configuration aswell.

Referring to FIG. 16, a top view of a portion of a rotor lamination 20portion of an electric machine 100 with a component 10 is shown. FIG. 16depicts a rotor lamination 20 of a single layer, four-pole IPM 100having straight permanent magnets 40 therein. (The embodiment is similarin aspects to the embodiment shown in FIGS. 3A and 3B). As shown andknown in the art, the rotor lamination 20 includes a plurality of statorwindings (not shown) and inboard of the stator windings are disposed oneor more permanent magnets 40 located in one or more openings 22 in therotor lamination 20. Once the permanent magnets 40 are disposed withinthe openings 22 there typically remains adjacent to either end of thepermanent magnets 40 an opening 24.

The plurality of rotor bars 14 are disposed in the plurality of openings24 longitudinally through the stack of rotor laminations 20. At or neareither end of the stack of rotor laminations 20 are connection elements16 that are connected to both ends of the rotor bars 14. In thisembodiment, one or more ring 12 (i.e., rotor bars 14 and connectionelements 16) is split into two or more rings 12. As shown, there are tworotor bars 14 placed in the openings 24, and there are two connectionelements 16 connecting the two rotor bars 14. In this manner, thecomponent 10 embodiment in FIG. 16 has four rotor loops 12 where eachloop 12 is constructed of four rotor bars 14 and four connectionelements 16 for the particular machine 100. By splitting the loops intomultiple loops (term “split rotor bar” configuration) fault tolerance isprovided. As long as at least one loop in the plurality of loops remainsfunctional, the ring 12 will be able to introduce the desired ringsaliency. It should be apparent that under aspects of the presentinvention that various configurations of splitting, via design, aconnection element 16, rotor bar 14, loop 12, and/or cage 13 into two ormore elements other than that shown is possible. For example, theelements may be in other quantities than just two (as depicted in FIG.16.

Referring collectively to FIGS. 17A, 17B, 17, and 18, schematic diagramsof perspective views of various embodiments showing the installation ofa portion of a component 10 in a machine 100 in accordance with aspectsof the present invention. While FIG. 17A shows a partial installation ofan element, while FIG. 17B shows the completed installation of theelement from FIG. 17A. A U-shaped element, which may be pre-formed(e.g., bent), is made of a conductive, non-magnetic material comprisingtwo rotor bars 12 connected via a connection element 16. The U-shapedelement may be inserted into two openings (e.g., 24) in the rotor 90 ofthe machine 100 (not fully shown). As shown, each of the rotor bars 14has extensions 15 that extend beyond the length of the rotor core 90 ofthe machine 100. The extensions 15 may then be bent and connectedtogether to form a second connection element 16, thereby forming acompleted ring 12, as shown in FIG. 17B. The extensions 15 may beconnected by any known method including, but not limited to, brazing,welding, mechanically fastening, and the like.

Referring to the embodiment shown in FIG. 18, a U-shaped element(similar to the embodiment discussed in FIG. 17A) comprising element,which may be pre-formed (e.g., bent), is made of a conductive,non-magnetic material comprising two rotor bars 12 connected via aconnection element 16. The U-shaped element may be inserted into twoopenings (e.g., 24) in the rotor 90 of the machine 100 (not entirelyshown). As shown, each of the rotor bars 14 has extensions 15 thatextend beyond the length of the rotor 90 of the machine 100. In atypical embodiment, the extensions 15 of the embodiment in FIG. 18 donot need to be as long as the extensions 15 of the embodiment in FIG.17A. A small U-shaped end piece 18, made of a conductive material,having extensions 15 may be placed so that the respective extensions 15of the end piece 18 and the U-shaped element are adjacent to each other.The extensions 15 may be connected by suitable means (e.g., brazing,welding, mechanical fastening, etc.) thereby creating a loop 12. Itshould be noted that the end piece need not be U-shaped as discussedabove. For example, in another embodiment, a straight element likeconnection element 16 without extensions 15 may be used in lieu of theU-shaped end piece 18, wherein the connection element 16 is attached tothe U-shaped element and connected thereto.

Referring to the embodiment shown in FIG. 19, a U-shaped element(similar to the embodiment discussed in FIG. 18) comprising element,which may be pre-formed (e.g., bent), is made of a conductive,non-magnetic material comprising two rotor bars 12 connected via aconnection element 16. The U-shaped element may be inserted into twoopenings (e.g., 24) in the rotor 90 of the machine 100. As shown, eachof the rotor bars 14 has extensions 15 that extend beyond the length ofthe rotor 90 of the machine 100. In a typical embodiment, the extensions15 of the embodiment in FIG. 19 do not need to be as long as theextensions 15 of the embodiment in FIG. 17A. A full-ring connector 17,made of conductive material, may be placed so that the extensions 15 ofthe U-shaped element are adjacent to and/or extending through theconnector 17. The extensions 15 and/or rotor bars 14 may be connected tothe connector 17 by suitable means (e.g., brazing, welding, mechanicalfastening, etc.) thereby creating a loop 12.

Referring to FIG. 20, a schematic diagram of a perspective view of acomponent 10 according to an aspect of the present invention is shown.The d-axis (direct axis) and the q-axis (quadrature axis) are denoted byarrows labeled “d” and “q”, respectively. As shown, the component 10includes four rotor loops or rings 12. Each ring 12 comprises two rotorbars 14 connected at one end to a connector element 16. The other endsof the rotor bars 14 are connected to a single full ring connector 17.In this manner, all rings 12 are effectively connected to the full ringconnector 17, thereby defining a cage 13. There are a total of eightrotor bars 14 for the element 10. In this manner, the four loops 12,being interconnected, effectively define a cage 13. As shown, theapproximate midpoint of a loop 12 aligns with the d-axis. In otherwords, a loop 12 is substantially concentric with the d-axis. Similarly,the q-axis substantially aligns with a midpoint between two adjacentrotor bars 14.

While various embodiments discussed herein have general disclosedmagnets 40 and openings 22 of specific sizes and configurations, itshould be apparent that different quantities, shapes, and configurationsthat those illustrated may be used without departing from aspects of thepresent invention. For example, the openings 22 and/or magnets 40 may beother shapes other than straight including, for example, curved,trapezoidal, round, and the like, and combinations thereof.

While various embodiments discussed herein have general disclosed rotorconductors (e.g., rotor bars 14) disposed in openings 24 adjacent tomagnets 40 in the rotor lamination 20, it should be apparent that underaspects of the present invention that the rotor conductors, in certainembodiments, are disposed in openings and/or voids (e.g., grooves,channels, gaps, etc.) on the outer portion 90 of the rotor. In otherwords, in embodiments the rotor conductors may be placed in a locationsuch that, at least initially, is not fully surrounded by rotorlamination material.

Finite-element analysis based modeling was conducting on various modelsof machines, both for electric machines not having any rotor circuitstructure (i.e., related art) and for electric machines usingembodiments of the rotor circuit structures of the present invention.Some results of the modeling are illustrated in FIGS. 21-24 herein.

Small signal saliency and small signal saliency angle is key informationused for sensorless control, under aspects of the present invention, andit is defined using small signal impedance. Small signal impedance isdefined for a small high frequency variation of current (Δi_(d), Δi_(q))from the operating point current vector (i_(d), i_(q)). Small signalimpedance varies depending on the orientation of the high frequencycurrent variation (Δi_(d), Δi_(q)). Small signal saliency at a givenoperating point (Δi_(d), Δi_(q)) is the ratio of the maximum smallsignal impedance to the minimum small signal impedance over a full rangeof orientation of the high frequency current variation. Small signalsaliency is greater than or equal to 1, and it is desired to be muchlarger than 1 for suitable sensorless control performance. Small signalsaliency angle is the angular displacement of the maximum small signalimpedance orientation from the rotor reference frame, for example theq-axis of the rotor reference frame. The small signal saliency angle isdesired to be constant over the operating range, near zero for example,in order to achieve desired encoderless control performance.

Referring to FIG. 21, a graph showing the small signal saliency on thecurrent vector (i_(d), i_(q)) plane for an IPM machine of the relatedart is depicted as element 300. Contrastingly, FIG. 22 shows the contourplots of small signal saliency of an IPM machine incorporating thecomponent in accordance with the present invention as element 350. Asshown in the graph, the resultant saliency is improved and increased ascompared to the saliency in the related art machine (FIG. 21).

Referring to FIG. 23, a graph showing the contour plots of small signalsaliency angle on the current vector (i_(d), i_(q)) plane an IPM machineof the related art is depicted as element 400. Contrastingly, FIG. 24shows the contour plots of small signal saliency angle of an IPM machineincorporating the component in accordance with the present invention aselement 450. As shown in the graph, the resultant wide angular margin byusing the component as compared to the related art machine (FIG. 23)depicting the very tight saliency angle.

Referring to FIG. 23, a graph showing the contour plots of small signalsaliency angle on the current vector (id, iq) plane an IPM machine ofthe related art is depicted as element 400. Contrastingly, FIG. 24 showsthe contour plots of small signal saliency angle of an IPM machineincorporating the component in accordance with the present invention aselement 450. As shown in the graph, the resultant wide angular margin byusing the component as compared to the related art machine (FIG. 23)depicting the very tight saliency angle.

FIG. 25 shows a graph that depicts speed (%) on a x-axis vs. torque (%)on a y-axis. As shown, when a machine uses the component of the presentinvention the performance of the machine may reach the upper-leftportion (i.e., dark upward pointing arrow) of the graph. That is byemploying aspects of the present invention, full torque capability atlower machine speeds is attainable. (For example, an electric machine ofthe present invention may reach 50% of torque capability at speeds below10% of the rated speed of the machine. In other embodiments, theelectric machine may reach over 75% of torque capability at speeds below10% of the rated speed of the machine. In still other embodiments, theelectric machine may reach over 90% of torque capability at speeds below10% of the rated speed of the machine. In still other embodiments, theelectric machine may reach 100% of torque capability at speeds below 10%of the rated speed of the machine.)

Under aspects of the present invention, the components 10 and theelectric machines 100 discussed herein may be used as a traction motorfor virtually any vehicle. A vehicle support frame connected to the oneor more electric machine 100. Suitable vehicles for use include, but arenot limited to, an off-highway vehicle (OHV), a locomotive, a miningvehicle, electric-motorized railcar, automobiles, trucks, constructionvehicles, agricultural vehicles, airport ground service vehicles,fork-lifts, non-tactical military vehicles, tactical military vehicles,golf carts, motorcycles, mopeds, all-terrain vehicles, and the like.

While the embodiments illustrated and described generally herein haveshown that the electric machine 100 to be an interior permanent magnet(IPM) machine, other electric machines than those illustrated herein mayemploy aspects of the present invention including, for example, PMSRM,SRM, and induction machine, and the like. Various embodiments of therotor circuit component 10 may be used in these various other types ofelectric machines.

Therefore, in accordance with one aspect of the invention, a rotorcomponent comprises a rotor circuit configured for use with one of aninterior permanent magnet (IPM) machine and a synchronous reluctancemachine (SRM), the rotor circuit comprising: at least one pole circuit,wherein the at least one pole circuit are made of a conductive,non-magnetic material.

In accordance with another aspect of the invention, an electric machinecomprises a rotor core comprising magnetic steel; a stator configuredwith a plurality of stationary windings therein; a plurality of openingsdisposed within or on the rotor core; and a rotor circuit configured tointroduce saliency based on an orientation of a portion of the rotorcircuit in relationship to a pole location of the electric machine, saidrotor circuit made of a conductive, non-magnetic material.

In accordance with another aspect of the invention, an electric machinecomprises: a rotor core; a stator configured with a plurality ofstationary windings therein; a plurality of openings disposed within therotor core; and a rotor circuit structure comprising at least one polecircuit disposed in a predetermined location, wherein said predeterminedlocation is in range that extends from about a q-axis to about a d-axisof the electric machine.

In accordance with another aspect of the invention, an electric machinecomprising: a rotor core; a stator configured with a plurality ofstationary windings therein; a plurality of openings disposed within therotor core; a rotatable shaft therethrough; and a rotor circuitstructure comprising at least one loop or ring of a conductive,non-magnetic material, wherein said at least one loop or ring issubstantially concentric about a d-axis of the electric machine.

In accordance with another aspect of the invention, an interiorpermanent magnet (IPM) machine comprises a means for convertingelectrical energy to rotational energy; and a means for providingincreased magnetic saliency at high frequency excitation.

While only certain features of the invention have been illustratedand/or described herein, many modifications and changes will occur tothose skilled in the art. Although individual embodiments are discussed,the present invention covers all combination of all of thoseembodiments. It is understood that the appended claims are intended tocover all such modification and changes as fall within the intent of theinvention.

What is claimed is:
 1. An electric machine comprising: a rotor corecomprising magnetic steel; a stator configured with a plurality ofstationary windings therein; a plurality of openings disposed within oron the rotor core; a plurality of permanent magnets disposed in theplurality of openings; and a rotor circuit configured to introducesaliency based on an orientation of a portion of the rotor circuit inrelationship to a pole location of the electric machine, said rotorcircuit made of a conductive, non-magnetic material, wherein a portionof the rotor circuit and the plurality of permanent magnets are disposedin the same plurality of openings.
 2. The electric machine of claim 1,wherein the plurality of permanent magnets are disposed in a pluralityof rows.
 3. The electric machine of claim 1, wherein the electricmachine is one of an interior permanent magnet (IPM) machine and apermanent magnet (PM) machine.
 4. The electric machine of claim 3, theIPM machine comprising one of a single layer IPM, a multi-layer IPM, anda spoke-type IPM.
 5. The electric machine of claim 1, wherein theelectric machine comprises a traction motor.
 6. The electric machine ofclaim 1, wherein the rotor circuit comprises a plurality of rotorconductors connected to a plurality of connection elements.
 7. Theelectric machine of claim 6, wherein at least one of the plurality ofrotor conductors comprise one of a rotor bar, a multi-stranded bar, amulti-stranded wire, and a litz wire.
 8. The electric machine of claim6, wherein a cross-sectional shape of the plurality of rotor conductorsis contoured to fit a shape of the plurality of openings.
 9. Theelectric machine of claim 1, wherein the rotor circuit defines aconfiguration of at least one of a loop, a shifted loop, a cage, ashifted cage, and combinations thereof.
 10. The electric machine ofclaim 1, the rotor circuit comprising a plurality of rotor conductorsand one or more connection elements, wherein the plurality of rotorconductors are disposed in a plurality of openings adjacent theplurality of permanent magnets.
 11. The electric machine of claim 10,further wherein the plurality of rotor conductors is disposed in one ofthe plurality of openings.
 12. The electric machine of claim 1, therotor circuit comprising at least one pole circuit.
 13. The electricmachine of claim 12, wherein the at least one pole circuit comprises aplurality of pole circuits.
 14. The electric machine of claim 12,wherein a quantity of the at least one pole circuit equals a quantity ofpoles.
 15. The electric machine of claim 1, further comprising a shaftconfigured to rotate within the electric machine.
 16. The electricmachine of claim 1, the rotor core further comprising a plurality oflaminations.
 17. The electric machine of claim 16, the plurality ofopenings disposed through the plurality of laminations.
 18. A vehiclecomprising at least one electric machine of claim 1 thereon, saidelectric machine configured as a traction motor; and a vehicle supportframe connected to said electric machine.
 19. The vehicle of claim 18,wherein the vehicle comprises one of an off-highway vehicle (OHV), alocomotive, a mining vehicle, and an electric-motorized railcar.